Method to prevent or reduce formation of magnetism in two adjacently located saw blades rotating in opposed directions, and a device for utilization of the method

ABSTRACT

A method and device for preventing or reducing formation of magnetism in two adjacently located saw blades rotating in opposed rotary directions in relation to each other. Each saw blade is arranged having a number of substantially radially extending through grooves having an extension within the area of the rotary center for each saw blade and the surrounding saw teeth area. The grooves are arranged, when rotating, to remove air existing between adjacent planes of the saw blades. The through grooves are arranged having a substantially curved extension, but may also have a substantially linear extension. The grooves are arranged having a chamfer by the edge portions, arranged to increase removal of air from the space between the interacting saw blades.

FIELD OF THE INVENTION

The present invention relates to a method for preventing or reducingformation of magnetism in two adjacently located saw blades rotating inopposed rotary directions in relation to each other, and a device forutilization of the method

BACKGROUND OF THE INVENTION

SE, B, 458 096 discloses a pair of saw blades, comprising two inrelation to each other adjacently located saw blades, arranged whilerotating in relation to each other opposed rotary directions to take upa saw cut in a workpiece in a common and interacting operation.According to this prior patent publication internal contact between thesaw blades is prevented by application of a pneumatic or hydraulicpressure Ad between the saw blades. To accomplish such a pneumaticpressure, it is proposed that each saw blade is arranged with embossedportions from an outer side plane, arranged to form channels openagainst the rotary direction. Further improvements of such aninteracting pair of saw blades are proposed in SE Patent Appln. No.9403767-8, primarily intended to improve the cut surface of a workpieceand to reduce burr formation, but also this embodiment is based on thatthe pair of interacting saw blades are maintained separated byapplication of a pneumatic or hydraulic pressure.

However, practical use of the above mentioned previously known sawblades has resulted in a previously unknown and non-desirable technicaleffect. The adjacently located and in relation to each other opposeddirections rotating saw blades have been magnetized in use, and sinceadjacent surfaces have a machined plane surface, the saw blades havewhen used magnetically adhered to each other with such a force, thatthey hardly not have been separable from each other. The successivelyincreased magnetization during operation has also resulted in aconsiderable rotary speed reduction, and the sawing operation has beeninterrupted in certain cases. During the starting operation, a certain“wobbling effect” has been observed for the saw blades, i.e.oscillations which during an initial stage result in a wider saw cut.

SUMMARY OF THE INVENTION

The object of the present invention is to disclose a method for reducingformation of magnetism in a pair of saw blades of the above mentionedtype, which during a starting phase also results in that the adjacentlylocated saw blades move in a parallel relationship, without the abovementioned oscillating movements in relation to each other. The inventionalso relates to a device for utilization of the method.

The method according to the present invention for preventing or reducingformation of magnetism in two adjacently located saw blades rotating inopposed rotary directions in relation to each other is mainlycharacterized in that each saw blade is arranged having a number ofsubstantially radially extending through grooves having an extensionwithin the area of the rotary centre for each saw blade and thesurrounding saw teeth area, arranged when rotating to remove airexisting between adjacent planes of the saw blades, and thereby preventor reduce magnetization of the saw blades.

The device for utilization of the method according to the presentinvention is mainly characterized in that each saw blade is arrangedhaving a number of substantially radially extending through grooveshaving an extension within the area of the rotary centre for each sawblade and the surrounding saw teeth area, arranged when rotating toremove air existing between adjacent planes of the saw blades.

BRIEF DESCRIPTION OF THE DRAWINGS

The method according to the present invention and a nonrestrictingexample of an embodiment for utilization of the method are more fullydescribed below with reference to the accompanying drawings, in which:

FIG. 1 shows a side view of a saw blade forming a part of an interactingpair of saw blades, viewed from the side which is adjacent to aninteracting saw blade and arranged with an example of an embodimentaccording to the invention;

FIG. 2 shows a cross-sectional view in enlarged scale at the line II—IIin FIG. 1;

FIG. 3 shows a view corresponding to FIG. 2 disclosing two interactingsaw blades rotating in opposed directions in relation to each other;

FIG. 4 shows a side view of a modified embodiment of a saw bladeaccording to the present invention, viewed from the side which isadjacent to an interacting saw blade;

FIG. 5 shows a cross-sectional view in enlarged scale at the line V—V inFIG. 4;

FIG. 6 shows a cross-sectional view in enlarged scale through parts oftwo interacting saw blades according to the present invention, intendedto illustrate an example of how the non-penetrating grooves can bearranged displaced in relation to each other at the two saw blades;

FIG. 7 shows a side view of a further modified embodiment of a saw bladeaccording to the present invention, viewed from the side which isadjacent to an interacting saw blade;

FIG. 8 shows a view corresponding to FIG. 7 of an example of a furthermodified saw blade according to the present invention;

FIG. 9 shows a cross-sectional view in enlarged scale of a saw bladeaccording to the present invention at the line A—A in FIG. 7 or FIG. 8;

FIG. 10 shows a cross-sectional view in enlarged scale of the saw bladeshown in FIG. 7 at the line B—B;

FIG. 11 is a cross-sectional view of two adjacently located saw blades,intended to show exaggeratedly how the saw blades can be deflected awayfrom each other when sawing;

FIG. 12 is a view corresponding to FIG. 11 which shows exaggeratedly amodification intended to remove the problem shown in FIG. 11;

FIG. 13 is a cross-sectional view in enlarged scale of the areadenominated XIII in FIG. 11; and

FIG. 14 is a side view showing two adjacently located saw teeth modifiedaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The problem with strong magnetization of two adjacently located sawblades rotating in opposed directions may be related to ionization ofintermediately located air molecules in association with formation of amagnetic/electrical changing field, and this phenomena also influencesthe saw blades during an initial start phase, and as a result, the sawblades do not move in a parallel relationship to each other.

In previously known solutions, as mentioned earlier, the saw blades havebeen regarded as stable in relation to each other, e.g. by arranging airchannels in the saw blades, which when rotated supply air to the spacebetween the saw blades, and thus stabilize same during a sawingoperation by means of a pneumatic force.

The method according to the present invention is based on an importantand in this connection surprising change of previously acceptedtechnology, namely to remove air existing between the saw blades bymeans of preferably substantially radially extending through penetratinggrooves in the area between the central portion of the saw blades andthe saw teeth area.

Theoretically, such an action should result in that the saw blades arepressed towards each other, and presumably that same should be furthermagnetized, e.g. by means of frictional influence.

However, the method according to the present invention results in asurprising effect, on one hand magnetization of the saw blades isavoided (substantially totally), and on the other hand the saw bladesreceive a stable and parallel motion when commencing rotation in opposedrotary directions. As a further surprising effect, the saw blades willmaintain an adjacent, but separated, relationship.

With reference to FIG. 1, an example of an embodiment for utilization ofthe method according to the present invention is shown. A saw blade, inits entirety denominated 1, is arranged with a number of substantiallyradially extending through grooves 2, 2′, 21″, preferably substantiallyequally angularly separated from each other. In the shown example of anembodiment the grooves 2, 2′, 2″ have a slightly bent curved extension,with each end portion located as a first portion in the rotary directionof the saw blade 1, and with the central portion as a successivelyfollowing part. This configuration is a preferred configuration, butalso opposed extension, or a substantially linear extension, can beused.

The effect of these grooves can be further increased, which initially isdescribed with reference to FIG. 2. In order to further disclose whichplane that is located adjacent to an interacting saw blade, same hasbeen denomitated “N”, whereas the plane which in use acts as an outer oroutside plane is denominated “U”. A groove 2 is shown in cross-section,disclosing that the grooves 2, 2′, 2″ have a chamfer 3 at the edgeportion which is a first edge portion in the rotary direction, and thatthe grooves 2, 2′, 2″ have a chamfer 4 in the same direction at the edgeportion serving as a final edge portion in the rotary direction. Thelatter chamfer 4 extends from the inner side plane and is inclinedtowards the outer side plane, whereas the first chamfer 3 is terminatedby the edge portion of the grooves 2, 2′, 2″ which is located by theouter plane of the saw blade 1.

These chamfers 3, 4 cause during rotation of the saw blade 1 removal ofair existing by the inside plane of the saw blade 1, i.e. the planewhich is adjacent to an interacting saw blade 1′.

This is shown more in detail in FIG. 3, which shows a portion of two sawblades 1, 1′ rotating in an opposed and adjacent relationship. Thisfigure illustrates how the grooves 2, 2′, 2″ during rotation of the sawblades 1, 1′ remove intermediately existing air, an action resulting inthat magnetization of the saw blades 1, 1′ is avoided, and that the sawblades 1, 1′ receive a stable and parallel movement during the initialstage of a sawing operation. Previously discussed chamfers 3, 4 resultin accomplishment of an increased removal of air, but an acceptablereduction of magnetization of the saw blades 1, 1′ is also accomplishedwithout such chamfers.

As an example of a preferred embodiment five grooves 2, 2′, 2″ having agroove width of 3 mm were arranged, and with chamfers 3, 4 arrangedhaving an angle of 45°. A pair of saw blades (diameter 225 mm) arrangedaccordingly have not resulted in magnetization of the saw blades 1, 1′within the rotary range of 2,000-4,700 rpm.

Tests have also been made without chamfers 3, 4, and at a number ofrevolutions of 2,000 rpm disclosed that a groove width of at least 4.8mm for the grooves 2, 2′, 2″ was required to prevent magnetization. Whenthe number of revolutions was increased to 4,700 rpm a groove width ofat least 6 mm was required to avoid magnetization, i.e. an increasedgroove width is required for an increased rotary speed.

It is also possible to reduce the groove width under 3 mm by changingthe angle of the chamfers 3, 4. In this case the chamfers 3, 4 are givena more pointed angle, reduced approximately 3° for each one millimeterreduction of the groove width, i.e. approximately 42° for a groove widthof 2 mm, and approximately 39° for a groove width of 1 mm. Chamfershaving a more blunt angle than 45° result in a considerably more poorresult, and as a result, the width of the grooves 2, 2′, 2″ can not bereduced as described.

Above described examples of various embodiments disclose that a numberof variables exist with regard to the design of the grooves 2, 2′, 2″,which can be varied to accomplish desired result. Apart from what hasbeen exemplified, the number of grooves obviously constitute a furthervariable, and the exemplified embodiments include five grooves 2, 2′,2″, substantially equally spaced from each other by an angle having thesize of 72°. Reduction or increase of the number of grooves 2, 2′, 2″can thus be compensated by an increase/reduction of the width of thegrooves 2, 2′, 2″, and the width of the grooves can be further reducedby previously mentioned chamfers. Also utilized rotary speed has acertain influence on the width of the grooves, particularly when theedge portions of the grooves 2, 2′, 2″ are not arranged with chamfers,resulting, as previously mentioned, in a need for a larger groove widthfor an increased rotary speed.

A modified embodiment of a saw blade in relation to FIGS. 1-3 is shownin FIGS. 4 and 5 which in similarity with the previously describedembodiment includes a number of substantially radially extending throughgrooves 2, 2′, 2″, preferably substantially equally angularly spacedfrom each other. In the example of an embodiment shown, the grooves 2,2′, 2″ have a slightly bent curved extension, with each end portionlocated as an initial first portion in the rotary direction of the sawblade 1, and with the central portion as a successively following part.This configuration constitutes a preferred configuration, but also areversed extension, or a substantially linear extension, can be used.

This results in previously discussed advantages and furthermore thevacuum formed between two interacting saw blades is reduced, and alsothe nondesirable increase of temperature for the saw blades during therotary movement of same. Said increase of temperature causes a wideningof the gap between the outer parts of the saw blades since the sawblades tend to bend away from each other, a condition which results insaw dust and other particles can penetrating in between the interactingsaw blades.

The effect of the grooves 2, 2′, 2″ is increased by a number ofnon-penetrating grooves or recesses 5, 5′, 5″, which are arranged by theplane of the saw blade intended to serve as an adjacent surface inrelation to an interacting saw blade. According to a preferredembodiment (FIG. 4) the non-penetrating grooves 5, 5′, 5″ extendradially from each other with a different radius from the centre of thesaw blade 1.

The non-penetrating grooves 5, 5′, 5″ have a relatively small depth,e.g. 0.1 mm, but this depth can be varied from a few hundreds of amillimeter to a few tenths of a millimeter, and even deeper grooves 5,5′, 5″ may be used for saw blades having very large diameter. As anexample, tests have been performed with extremely good result utilizinga saw blade 1 having a diameter of 230 mm and 7-9 non-penetratinggrooves 5, 5′, 5″ with a width of 2 mm and a depth of 0.1 mm or less.

However, suitable width/depth for the non-penetrating grooves 5, 5′, 5″,space between the grooves and number of grooves, can obviously be variedwithin broad limits and with regard taken to the diameter of the sawblade, rotary speed and similar factors.

FIG. 6 is intended to disclose how the grooves 5, 5′, 5″ can be arrangeddisplaced in relation to each other at two interacting saw blades 1, 1′.Such a relative displacement results in an improved result, but itshould be emphasized that the shown degree of displacement can besmaller, and that a fully acceptable result also can be obtained withthe grooves 5, 5′, 5″ located in a substantially opposed relationship.

In this connection, it should also be emphasized, that even a previousembodiment refers to the non-penetrating grooves 5, 5′, 5″ as a numberof grooves, said number may also be reduced to only one circular groove.However, an embodiment with only one circular non-penetrating groove hasobviously not the same good properties as an embodiment having severalsuch grooves 5, 5′, 5″, but even a single groove results in a certaintechnical effect.

Examples of further modified embodiments are shown in FIGS. 7 and 8,intended to increase the effect of previously discussed through grooves2, 2′, 2″ by a number of non-penetrating grooves or recesses 5, 5′, 5″,which are arranged by the plane of the saw blade 1 which is intended tobe an adjacent surface in relation to an interacting saw blade.According to a preferred embodiment (FIG. 7), the non-penetratinggrooves 5, 5′, 5″ extend curved with a common radius from the centre ofthe saw blade 1 and having an angular extension which is less than thedistance between each other adjacently located through grooves 2, 2′,2″. Each non-penetrating groove 5, 5′, 5″ extends from a through groove2, 2′, 2″ in the rotary direction of the saw blade 1 (as indicated by anarrow) and is terminated by a closed end portion before the next throughgroove 2, 2′, 2″.

The non-penetrating grooves 5, 5′, 5″ have a relatively small depth,e.g. 0.1 mm, but this depth can be varied from a few hundreds of amillimeter to a few tenths of a millimeter, and for saw blades having avery large diameter even deeper grooves 5, 5′, 5″ can be used. As anexample, extremely good results were obtained with a saw blade 1 havinga diameter of 230 mm and non-penetrating grooves with a width of 20 mmand a depth of 0.1 mm. Good results were also obtained when the width ofthe grooves was reduced to 10 mm.

However, suitable width/depth of the non-penetrating grooves 5, 5′, 5″can obviously be varied within broad limits, related to the diameter ofthe saw blade 1, rotary speed and similar factors.

Even if the non-penetrating grooves 5, 5′, 5″ have a further restrictedextension, i.e. when the grooves 5, 5′, 5″ do not communicate with thethrough grooves 2, 2′, 2″, an acceptable technical effect is obtained.An example of such an embodiment is shown in FIG. 8, with thenon-penetrating grooves 5, 5′, 5″ having closed end portions, i.e. notdirectly communicating with a through groove 2, 2′, 2″.

Even though not shown in the drawings, the non-penetrating grooves 5,5′, 5″ shown in FIGS. 7 and 8 may for example be replaced by two or morepreferably substantially parallel grooves, i.e. with, in relation toeach other, different radius. In such an embodiment the groove width foreach individual non-penetrating groove 5, 5′, 5″ can obviously alsousually be reduced in relation to embodiments having only one groove 5,5′, 5″.

The non-penetrating grooves 5, 5′, 5″ can also be used in associationwith through grooves 2, 2′, 2″ having chamfered side portions, i.e.arranged as disclosed in the embodiment according to FIGS. 1-3.

It is also within the scope of the invention to arrange thenon-penetrating grooves 5, 5′, 5″ in such a way, that the grooves 5, 5′,5″ extend between two adjacently located through grooves 2, 2′, 2″, i.e.with each end portion open towards said through grooves 2, 2′, 2″. Suchan embodiment substantially corresponds to the embodiment previouslydescribed with reference to FIGS. 4-6.

Furthermore, the non-penetrating grooves 5, 5′, 5″ can also be givenanother length extension different from what has been shown anddescribed, e.g. a more straight extension, even though the shown curvedextension obviously, from a machining point of view and other aspects,is a preferred embodiment.

As previously mentioned, the invention is not restricted to the examplesrelating to groove depth, groove width and number of grooves givenearlier, since the possibility exists to vary these parameters within alarge spectrum.

The saw blade 1 according to the present invention can be furthermodified in order to secure that the outer portion of the saw blade 1 isnot deflected away from an adjacent and interacting saw blade 1′ duringrotation, a situation which is shown exagerrated in FIG. 11.

By arranging the saw blades 1, 1′ as shown exagerrated in FIG. 12, i.e.shaped with facing surfaces having a substantially concave shape,existing contact surface is reduced considerably, which results inreduced magnetization of the saw blades 1, 1′, and also reducedtemperature increase. During a sawing operation the saw blades 1, 1′take up a more parallel extension, partly through rotary influence,partly through pressure from the saw cut surfaces formed.

Furthermore, the outer peripheral portions of the saw blades 1, 1′ arepreferably arranged with towards each other facing surfaces initially(prior to a sawing operation) extending in a substantially parallelrelationship, as indicated in FIG. 13 as the area “X”. This ispreferably accomplished by means of a grinding operation, and safeguardsthat the saw teeth do not intermesh during the rotary movement inopposed directions for the saw blades 1, 1′. As an example of theangular size which is ground off, an angle of 4-7 degrees., but the sizeof the angle is obviously adapted to the bowl shape of the saw blades 1,1′.

A further factor has been found influencing the magnetization of the sawblades 1, 1′, namely that magnetization is formed in the space forsawdust by the saw teeth. By arranging, as shown in FIG. 14, the bottompart (area “Z”) of the space for sawdust substantially straight orslightly curved and with the distance “Z” not smaller than 4 mm, saidmagnetization can be avoided.

The above modification can easily be implemented when manufacturing newsaw blades 1, 1′, as well as for existing saw blades 1, 1′, in order tofurther remove the problems obtained through magnetization of the sawblades 1, 1′.

The present invention is obviously in no way restricted to shown anddescribed examples of embodiments, but can be further modified. Forexample, shown examples of embodiments may in different ways be combinedwith each other within the scope of the inventive thought and thefollowing claims.

What is claimed is:
 1. Method for preventing or reducing formation ofmagnetism in two adjacently located saw blades rotating in opposedrotary directions in relation to each other, said method comprising:arranging each of the two adjacently located saw blades with each sawblade having a number of substantially radially extending throughgrooves located within an area between a rotary centre for each sawblade and a surrounding saw teeth area, and rotating the two adjacentlylocated saw blades in said opposed rotary directions to remove airexisting between adjacent planes of the two adjacently located sawblades, and thereby prevent or reduce magnetization of the twoadjacently located saw blades.
 2. Device for preventing or reducingformation of magnetism, said device comprising: two adjacently locatedsaw blades rotating in opposed rotary directions in relation to eachother, each saw blade having a number of substantially radiallyextending through grooves located within an area between a rotary centrefor each saw blade and a surrounding saw teeth area, said substantiallyradially extending through grooves being arranged to remove air existingbetween adjacent planes of the two adjacently located saw blades whenrotated in opposed rotary directions.
 3. Device according to claim 2,wherein the through grooves have a substantially curved extension havingend portions of the through grooves located in a rotary direction aheadof a central portion.
 4. Device according to claim 2, wherein thethrough grooves have a substantially linear extension.
 5. Deviceaccording to claim 2, wherein a width of the through grooves is largerfor saw blades intended for a higher rotary speed range than for sawblades intended for a lower rotary speed range.
 6. Device according toclaim 2, wherein the through grooves are arranged substantiallysymmetrically and angularly equally spaced from each other.
 7. Deviceaccording to claim 2, wherein the through grooves have a first edgeportion in the rotary direction forming an inclined edge surfaceextending from an outer plane of each saw blade towards an area definedby an inner plane located forward in the rotary direction, and thethrough grooves have a second edge portion at a successively followingedge portion to said first edge portion in said rotary direction with achamfer forming an inclined edge surface extending from the inner planeof each saw blade towards a successively following area of the outerplane in the rotary direction.
 8. Device according to claim 7, whereinthe chamfers are arranged having an angle of 45°.
 9. Device according toclaim 7, wherein a width of the through grooves is reduced by formingthe chamfers.
 10. Device according to claim 2, wherein the throughgrooves have a substantially perpendicular extension in relation to anouter plane of the saw blade.
 11. Device according to claim 2, whereinthe through grooves have a larger width for a number of grooves and asmaller width for a number of grooves.
 12. Device according to claim 2,wherein at least one non-penetrating groove having a curved extension isarranged at a side of each of the saw blades intended to serve as anadjacent side to the other saw blade.
 13. Device according to claim 12,wherein said non-penetrating groove is arranged extending between andcommunicating with the through grooves.
 14. Device according to claim12, wherein said non-penetrating groove is arranged extending betweenand with only one end portion communicating with said through groove.15. Device according to claim 12, wherein said non-penetrating groove isarranged extending between the through grooves, and with such anextension that said non-penetrating groove does not communicate with thethrough grooves.
 16. Device according to claim 2, wherein the saw bladeshave a substantially bowlshaped extension, facing side planes having asubstantially concave extension.
 17. Device according to claim 16,wherein the two saw blades are machined at a respective peripheralsurface facing each other to form a substantially parallel area. 18.Device according to claim 2, wherein a sawdust space in saw teeth of thesaw blades are arranged with a substantially straight or slightly curvedbottom area having an extension exceeding 4 mm.